It should work because I have worked with both 110V and 220V, but if you are too much worried you can get a voltage converter like 220Vto110V and make sure that it can at least provide 400 watts (or 500, you know just in case)

You can upgrade it to 4.3.1 and get untethered jailbreak, but as of this moment, iTunes will provide you with 4.3.2, for older firmwares go to http://www.felixbruns.de/iPod/firmware/ and download an older firmware. And I would like someone to correct me if posting this website requires permission or not.

What do you mean by "the sound comes through the ear phones and the speaker", I would assume that when you plug in your headphone, the music still plays through the speaker. Well in that case, there is something wrong with it. If your device is still under warranty, take it to apple for fixing or other wise try resetting the firmware by clicking restore option in itunes, hope that works.

There are several reasons, recently a friend of mine had the same problem because it was jailbroken (some stupid issues, may be) but later on I suggested him to go back to official firmware and the apps loaded. If you could tell me whether its jailbroken or not, I could be more specific

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